So, my friend has told me that rendertargets use alot of memory(more than textures even if same size), but I feel like he is referring to some weirdness within XNA not Monogame and it should be the same as a Texture2D, this scares me specifically because my current code base relies on a lot of Rendertargets specially my GUI system where for each form, which has its own Rendertarget for each one. Please some one clear the confusion?
Thanks 
Well, ask your friend to provide source, because that´s not true. Rendertargets take as much Vram as texture of same color depth - surface format (provided it is without any kind of DXT compression). To check for yourself use Nvidia Nsight to inspect Vram at runtime. Switching between rendertargets take some time but modern GPU deals with it pretty well and they have to since deferred rendering is currently most used approach. That being said, while in your case this approach might not mean any noticable performance difference (unless game itself has complex rendering pipeline and you have lot of GUI elements), it still doesn´t sound like ideal solution.
Thank you so much, you’ve relieved a lot of stress